1. Field of the Invention
The invention relates in general to a projector, and more particularly to a projector which provides an IR signal to detect whether an obstacle is positioned on an optical path of the projection light.
2. Description of the Related Art
In general, the projector includes a housing, a light engine and a light source. The light generated by the light source is projected to the light engine, which guides the light to the lens to project an image on the screen.
In the briefing, switching the operation mode of the projector is often required to users. Users often place an obstacle (such as a book or a piece of paper) in front of the lens of the projector to temporarily block the light projected via the lens of the projector in a simple way. However, the projection light of the projector has a certain level of intensity, and when the projection light of the projector is blocked by an obstacle, the projection light may be easily reflected to the lens of the projector and makes the lens overheated or even damaged.
Japanese Patent Publication No. 06-347748 discloses a technology of using a light emitter and a light receiver to detect whether an obstacle is positioned on the optical path of the projection light. In greater details, the light emitter emits a light signal, which is reflected to the light receiver via the obstacle on the optical path of the projection light. Thus, whether an obstacle is positioned on the optical path of the projection light can be determined according to the signal received by the light receiver. However, the light receiver disclosed in the prior art is merely for receiving the light signal provided by the light emitter. In other words, the only function of the light receiver is to receive the reflected light signal.